1. Field of the Invention
The present invention generally relates to communication devices, and more particularly, to a method and system for enabling optimized scanning in a mobile communication terminal with single/multi Subscriber Identity Module (SIM) cards with single radio frequency (RF).
2. Description of the Related Art
Mobile devices are typically able to detect the presence of one or more proximate mobile stations of various types, such as public land mobile networks (PLMNs), macro cells, micro cells, femto cells, pico cells, and the like. According to the existing technologies, the mobile device performs scanning process to identify and generate a list of available networks, from where the mobile device can select one of the network with which the mobile device can connect and initiate any type of mobile communication process. For example, PLMN list scanning can be conducted to generate a list of nearby PLMNs, Home PLMN (HPLMN)s, and closed subscriber groups (CSGs) or femto cells to the mobile device. The list generated by the PLMN list scan can be helpful during a PLMN selection, a HPLMN selection or a CSG selection.
According to existing technologies, if the PLMN list scan is performed during PLMN selection/HPLMN selection/CSG selection procedures, and any other scenario of manual PLMN selection/HPLMN selection/CSG selection procedures is immediately initiated, then the complete PLMN scan will be reinitiated. This situation arises usually in certain scenarios, such as when the user is in motion and moving from range of one mobile station to another, when the user is using a mobile device with dual or multi SIM cards, and the like. When the UE or mobile device has multiple/dual SIM cards with single radio frequency (RF) for performing the PLMN list scan, the RF has to be shared for a scanning operation on each SIM related operator. At this time, if any paging is received on another SIM, then the newly received paging will be missed. Thus, for each SIM present in the user equipment (UE), PLMN list scanning has to be performed separately, and therefore, each scanning operation for each SIM will increase the time taken to scan for the complete PLMN list. Further, a scanning operation for each SIM will consume more battery power.
The PLMN list acquisition procedures for different scenarios are described as below.
HPLMN timer expiration: The UE scans and generates a PLMN list after every HPLMN timer expiration, if UE is registered on the Visited PLMN (VPLMN). In the case of HPLMN timer expiration, the UE acquires a list of all available PLMNs from all the radio access technologies (RATs) depending on the mode of operation, such as, single mode, dual mode, tri mode, multi-mode, and the like, of the UE, based on the number of SIM present in the UE.
FIG. 1 is a flowchart illustrating an example for the HPLMN timer expiration procedure, according to the prior art. At step 102, the UE checks whether the HPLMN timer is expired. If the timer is expired, then the procedure proceeds to step 104, step 106, or step 108. At step 104, the UE checks whether the operating mode of the UE is a single mode comprising a single SIM. If the operating mode of the UE is a single mode, then at step 110, a list of all available PLMNs with respect to the respective RAT is acquired.
At step 106, the UE checks whether the operating mode of the UE is a double mode. If the operating mode of the UE is a double mode, then at step 112, a list of all available PLMNs with respect to the two respective RATs are acquired. At step 108, the UE checks whether the operating mode of the UE is a multi-mode (e.g., tri mode comprising three SIMs). If the operating mode of the UE is a multi-mode (e.g., tri mode), then at step 114, a list of all available PLMNs with respect to all (e.g., three) respective RATs are acquired.
Manual PLMN selection: Similar to the HPLMN timer expiration, for the manual PLMN selection procedure, a list of all available PLMNs has to be acquired from all RATs depending on the mode of operation, such as single mode, dual mode, tri mode, multi-mode, and the like, of the UE, based on the number of SIMs present in the UE.
FIG. 2 is a flowchart illustrating an example for the manual PLMN selection procedure, according to the prior art. At step 202, the UE checks whether the selection procedure is a manual PLMN selection procedure. If the selection procedure is a manual PLMN selection procedure, then the procedure proceeds to step 204, step 206, or step 208. At step 204, the UE checks whether the operating mode of the UE is a single mode operation involving a single SIM. If the operating mode of the UE is a single mode, then at step 210, a list of all available PLMNs with respect to the respective RAT is acquired.
At step 206, the UE checks whether the operating mode of the UE is a dual mode. If the operating mode of the UE is a dual mode, then at step 212, a list of all available PLMNs with respect to the two respective RATs are acquired. At step 208, the UE checks whether the operating mode of the UE is a multi mode (e.g., tri mode). If the operating mode of the UE is a multi mode (e.g., tri mode), then at step 214, a list of all available PLMNs with respect to all (e.g., three) respective RATs are acquired.
Periodic CSG selection: For the periodic CSG selection procedure, a list of all available PLMNs for CSG cells is acquired from all RATs depending on the mode of operation, such as, a single mode, a dual mode, a tri mode, a multi-mode, and the like, of the UE, based on the number of SIM present in the UE. Here, the acquired RATs exclude 2G RATs.
FIG. 3 is a flowchart illustrating an example for the periodic CSG selection procedure, according to the prior art. At step 302, the UE checks whether the selection procedure is a periodic CSG selection procedure. If the selection procedure is a periodic CSG selection procedure, then the procedure proceeds to step 304, step 306, or step 308. At step 304, the UE checks whether the operating mode of the UE is a single mode comprising a single SIM. If the operating mode of the UE is a single mode, then at step 310, a list of all available PLMNs with respect to the respective RAT, excluding 2G RATs, is acquired. At step 306, the UE checks whether the operating mode of the UE is a dual mode. If the operating mode of the UE is a dual mode, then at step 312, a list of all available PLMNs with respect to the two respective RATs, excluding 2G RATs, are acquired. At step 308, the UE checks whether the operating mode of the UE is a multi mode (e.g., tri mode). If the operating mode of the UE is a multi mode (e.g., tri mode), then at step 314, a list of all available PLMNs with respect to all (e.g., three) respective RATs, excluding 2G RATs, are acquired.
Based on the above-mentioned procedures, problems in different scenarios are identified in the description of how the manual periodic CSG selection along with any of the PLMN selection, the HPLMN timer expiration, and the periodic CSG selection are implemented in a short interval of time.
FIG. 4 is a flow diagram illustrating a problem in a scenario identified for a list acquisition procedure for periodic CSG timer expiration and HPLMN timer expiration, according to the prior art. FIG. 4 describes an interaction between Access Stratum (AS) 404 and Non Access Stratum (NAS) 402 in a multi-mode UE for generation and acquisition of a PLMN list. When a periodic CSG timer is expired at the NAS 402, then CSG search is initiated to get the available list of CSG IDentities (IDs) along with the PLMNs on all supported RATs (4G, 3G) by sending START_LIST_REQ to the AS 404. The AS 404 performs the scanning procedure and provides the CSG—Associated PLMN list in 4G and 3G RATs by sending LIST_IND to the NAS 402.
Assuming, an HPLMN timer expires immediately, NAS 402 again sends START_LIST_REQ to the AS 404 to acquire a list of all PLMNs for 4G, 3G and 2G RATs. Even though NAS 402 already has the list of available PLMNs which were acquired recently on 4G and 3G along with the CSG IDs (for the CSG cell), NAS 402 does not use the present PLMN list, but instead sends the request START_LIST_REQ for PLMN list again to get the corresponding list of available PLMNs from all RATs on 4G, 3G, and 2G. As the AS 404 again starts scanning procedures in 4G and 3G RATs, there will be a delay in acquiring the PLMN list, and thereby consuming more battery power. A similar problem can be observed when the PLMN list acquired due to the periodic CSG timer expiration and the manual PLMN selection is immediately triggered.
FIG. 5 is a flow diagram illustrating a problem in a scenario identified for a list acquisition procedure on two SIMs, when two SIMs with single RF have 4G and 3G RATs in common, according to the prior art. FIG. 5 describes an interaction between AS 504 and NAS 502 in a multi-mode UE with a dual SIM (SIM1 and SIM2), for generation and acquisition of the PLMN list. At the periodic CSG timer expiration, at the manual PLMN selection, or at the HPLMN timer expiration for SIM1, the UE needs to acquire the list of available PLMNs on SIM1. Here, SIM1 needs to acquire the PLMN list on 4G and 3G, and SIM2 needs to acquire the PLMN list on 4G, 3G, and 2G, so that both the SIM1 and SIM2 have 4G and 3G RATs in common. Upon expiration of a periodic CSG timer, the CSG search is initiated to get the available list of CSG IDs along with the PLMNs on all supported RATs on SIM1 by sending START_LIST_REQ to the AS 504. While the PLMN list request procedure is in progress at the AS 504 on SIM1, the RF will be used by SIM1.
During generation of the PLMN list on SIM1 after periodic CSG timer expiration, the HPLMN timer on SIM2 can expire. As the RF of the UE is being occupied by the SIM1, the UE has to wait until the release of the RF for sending a request for another PLMN list. The AS 504 generates the PLMN list on SIM1 and sends the LIST_IND on SIM1 to the NAS 502. Upon receiving the PLMN list, the RF is released by SIM1 for the use by SIM2. The SIM2 of the UE uses the RF channel and sends the START_LIST_REQ for acquiring a list of available PLMNs as part of the HPLMN timer expiration actions on all supported RATs of 4G, 3G, and 2G.
Even though SIM1 has already performed the PLMN list acquisition recently on 4G and 3G, and the RATs for which the PLMN list is acquired are also supported by SIM2, the available list of PLMNs already being present is not utilized and the PLMN list is acquired again. This leads to a delay in acquiring the PLMN list on SIM2 from 4G and 3G, in addition to the waiting time for the RF to be released by SIM1. Further, the delay in the release of RF and repeated generation of the PLMN list lead to consumption of more battery power.
FIG. 6 is a flow diagram illustrating a problem in a scenario identified for a list acquisition procedure on two SIMs with single RF, when two SIMs have 4G and 3G RATs in common, according to the prior art. FIG. 6 describes an interaction between AS 604 and NAS 602 in a multi-mode UE for generation and acquisition of a PLMN list. At the periodic CSG timer expiration, at the manual PLMN selection, or at the HPLMN timer expiration for SIM1, the UE needs to acquire the list of available PLMNs on SIM1. Here, the PLMN list required to be acquired by both the SIM1 and SIM2 are the same. Upon expiration of a periodic CSG timer, the CSG search is initiated to get the available list of CSG IDs along with the PLMNs on all supported RATs on SIM1 by sending START_LIST_REQ to the AS 604. While the PLMN list request procedure is in progress on SIM1, the RF will be used by SIM1.
During generation of the PLMN list on SIM1 after the periodic CSG Timer expiration, the periodic CSG Timer on SIM2 can expire. As the RF of the UE is being occupied by the SIM1, the UE has to wait until the release of the RF for sending request for another PLMN list. The AS 604 generates the PLMN list on SIM1 and sends the LIST_IND on SIM1 to the NAS 602. Upon receiving the PLMN list, the RF is released by SIM1 for the use by SIM2. The SIM2 of the UE uses the RF channel and sends the START_LIST_REQ for acquiring a list of available PLMNs as part of the periodic CSG timer expiration actions on all supported RATs.
Even though SIM1 has already performed the PLMN list acquisition recently on 4G and 3G, and the RATs for which the PLMN list is acquired are also supported by SIM2, the available list of PLMNs already being present is not utilized and the PLMN list is acquired again. This leads to a delay in acquiring the PLMN list on SIM2 from 4G and 3G, in addition to the waiting time for the RF to be released by SIM1. Further, the delay in the release of the RF and repeated generation of the PLMN list lead to consumption of more battery power.
The above-mentioned problems in different scenarios of the HPLMN timer expiration, the manual PLMN selection, and the periodic CSG selection are observed during the PLMN list acquisition in 3GPP based systems. The existing methodologies do not address the use of an existing PLMN list before the expiration of an HPLMN timer, and also do not address reducing battery power by reusing the same PLMN list before the expiration of the HPLMN timer.
Thus, there is a need of an effective method and system for optimized scanning in a mobile communication terminal to overcome the problems discussed above.